The present invention relates to classifying equipment in general, and more particularly, to an apparatus that separates preselected undersize object fractions, such as chunks, pellets, briquettes, aggregate, rocks, grain, seeds and the like from preselected oversized object fractions of the same or differing material.
Classifying devices are utilized to sort, grade and separate diverse sizes of commingled solids in a myriad of applications.
A relatively simple sorting device is represented by a screen. Depending on the chosen spacing of the mesh, a percentage of the solids of a desired maximum size are permitted to pass whereas the remaining larger components are restrained. Vibratory screens or grizzlies expedite the sorting process. Screens are prone to debilitating plugging and downtime.
For classifying larger objects, rotating drums having circumferentially spaced longitudinal bars permit desired sized objects to pass through the spacing of the bars for collection whereas the remaining larger articles continue through the drum.
Improvements to drum classifiers generally relate to complex mechanical mechanisms for moving the bars.
Representative designs include U.S. Pat. No. 2,984,351 to Van Slyck et al. wherein a plurality of sizing tubes or bars are rotatably mounted within rings.
U.S. Pat. No. 3,055,500 to Aubert-Maguero discloses a cylindrical cage having variable gaps between the bars to free jammed articles.
Bean graders of the type disclosed in U.S. Pat. No. 3,241,667 to Grosbety and U.S. Pat. No. 5,332,103 to Zittel disclose rotating drums having spring loaded spacing mechanisms for bars and rotatable grader bars respectively.
SU 1238-808 appears to be classifying drum suspended by springs.
U.S. Pat. No. 883,974 to Roughsedge discloses a rotating drum having rigid bars alternating with shiftable free bars constrained in space rings. The larger fractions are caused to erosively flow over an inner space ring as the drum rotates.
Applicants"" previous experience with a stationary grizzly resulted in significant exasperating and expensive downtime. Assignee produces carbonyl nickel pellets. Fused nickel pellet chunks (called xe2x80x9celephantsxe2x80x9d) tended to clog up the grizzly wire screens upon their exit from a furnace. The operation had to be repeatedly stopped and the plugging elephants physically removed by hand. A review of drum designs revealed complicated mechanical classifiers (such as those referenced above) that would be expected to experience periodic jamming in dusty and dirty industrial environments.
There is provided a refreshingly simple but robust drum classifier or trommel that easily divides solids into larger and smaller sized fractions in a demanding duty environment.
The trommel is an open cylinder including a plurality of longitudinal rods extending between two opposed end plates. The ends of a plurality of selected shorter rods are affixed to one end plate whereas the opposing unattached ends of these selected rods float in an opposing ring disposed between the two end plates. As the drum rotates and the objects impact all of the rods, the selected rods oscillate and vibrate in essentially infinite degrees of freedom so as to continuously alter their spaced relationship with each other as well as their fixed rod neighbors. The infinitely continuous vibrating motion size screens the objects with reduced plugging.